L63 - Marconi - Valve Tube - Amplitrex Tested - S54

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Vendeur: jpcollectables-jpcollectables ✉️ (9.205) 99.8%, Lieu où se trouve: Ely, Cambridgeshire, GB, Lieu de livraison: WORLDWIDE et de nombreux autres pays, Numéro de l'objet: 183738074971 L63 - MARCONI - VALVE TUBE - AMPLITREX TESTED - S54.

TESTED ON AMPLITREX AT1000

ALL TUBES ARE TESTED ON MY AMPLITREX AT1000, WHICH IS A FULLY SERVICED, CALIBRATED MODERN DIGITAL TUBE TESTER.

FIXED BIAS MODE

*All my tubes are tested under Fixed bias mode *

B+ is applied to the tube and then a fixed bias voltage is applied to the grid. This fixed voltage is obtained from the stored tube test settings. the bias voltage is set to the specification value. Plate current will be whatever the tube is capable of, at this fixed grid voltage.

 

TEST RESULTS

 

LOOK AT PICTURES.

 

GOOD OR BAD TUBE?

 

You may ask, what constitutes a “good” tube? Well, this is difficult to

say, and depends more upon your own criteria. In the days when vacuum

tubes were the mainstay, most component values and supply voltages could

be off as much as 20%, and the equipment would still work

satisfactorily. You can apply this rule to a minimum acceptable Emission

and Transconductance of 20% low, or a display of 80%. Tubes showing

emission or GM less than about 70% can be classified as bad. However,

you must be the one to determine for yourself if a tube with 70%

emission or GM is suitable for use or not. For example, a tube showing

70% may perform very poorly in one piece of equipment, yet be OK in

Another.

 

GAS TEST – mA Gas

Most tubes have some noise so expect approximately up to 2.5 mA  for even  a unused tube.  In radio receivers noise from a tube is likely to be less noticeable due to other factors. Compared to the desire for quality sound from audio amplifiers etc.

Preamp Tubes

In the case of a small preamp tube like a 12AX7 or EF86, anything

more than 0.1 milliampere of gas current will likely cause problems

in the application circuit. Noise may be excessive, and/or

the tube may not establish its correct operating point.

Power tubes

With power tubes a gasinduced

current increase of approximately less than 10 percent of normal plate current is OK in most application circuits.

 

Modern Manufacture Tubes

Some tubes of modern manufacture may show lower than “normal” grid

voltage (in Auto Bias Mode) or lower than normal plate current (in Fixed

Bias Mode), as some new tubes are not being manufactured to the same

standards as they were in the vintage years.

(Above text is for reference only. There are many opinions on preferred tube testing practices and how to interpret results. )

UK MAINLAND SHIPPING SERVICE MAY BE UPGRADED FREE OF CHARGE DEPENDING ON THE VALUE.

 

 


SHIPPING

UK MAINLAND FREE BUT SERVICE MAY BE UPGRADED FREE OF CHARGE DEPENDING ON THE VALUE.

EUROPE £15

REST OF WORLD £20

COMBINED SHIPPING AVALIBLE OUTSIDE OF UK

  • Condition: Occasion
  • Brand: Brimar

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